This invention relates generally to an improved power tool that includes a torque reaction bar. More particularly, but not by way of limitation, this invention relates to an improved power tool that includes a torque reaction bar and has a handle that can be positioned as desired relative to the tool housing.
In the use of power tools which have a rotating output shaft for driving nuts, threaded fasteners, drill bits, etc., reaction torque occurs which is particularly high upon the tightening of the nut or fastener, or in the event that the drill bit should stick. When such tools are used in mass production with many repetitive operations being performed, even a slight amount of reaction torque makes it difficult for the operator to be efficient and accurate. Therefore, it is desirable to remove all the reaction torque from the operator of the tool whenever possible.
In the past, power tools have been provided with reaction bars that are either manually held by the operator or placed in engagement with some convenient fixed object to prevent rotation of the housing due to the reaction torque. Such measures have succeeded in avoiding the imposition of extremely high torque loads on the operator. With such tools, however, it has been found that the tool handle, which generally contains the trigger, valve, etc. for operating the tool, may not be conveniently located when the reaction bar is engaged with the stationary object. Thus, another element of operator fatigue may be introduced when the tool is used on different types of assemblies.
To counter this problem, prior art devices such as, for example the tool described in U.S. Pat. No. 4,155,278 issued May 22, 1979 to Eugene M. Estok were constructed. That tool employes a swivel located between sections of the tool housing. One of the housing sections encompasses the speed reduction unit of the power tool, and the other encompasses the motor for driving the speed reducer. The use of the swivel has permitted the handle to be positioned as desired relative to the work piece, and thus substantially eliminated that element of operator fatigue.
However, the reaction torque is not entirely eliminated, although a large portion of it is absorbed by the torque reaction bar and prevented from reaching the operator due to the swivel. As noted in the patent, a portion of the reaction torque is still transmitted through the motor to the handle despite the swivel connection and, thus, is imposed on the operator. Again, it must be remembered that the repetitive nature of assembly operations is such that even the imposition of slight amount of torque may seriously fatigue the operator and interfer with his efficiency and accuracy.